'Battery-Backed' solar installation

[OceanArcher]

Here in South Mississippi, it seems like people are looking at a 'Battery-Backed' system for their homes, to assist their existing grid power connection. In the rural areas, power outages are a common thing. People are relocating their 120v circuits to a sub-panel driven by a solar-powered inverter and battery combination in an effort to minimize those outages. Granted, a system like this does not support the major loads such as A/C, water heating, cooking, etc, but if you have ever experienced our severe weather, having access to a small window air conditioner and low-power pump for the water well along with keeping the refrigerator cold is a fantastic thing ...

[ChrisOlson]

That's how us off-grid folks live all the time. We have all the major loads covered here, without utility power - A/C, electric water heating, electric cooking, and even electric clothes dryer. It just requires a bit bigger investment in equipment.

[Sunking]

What a horrible waste of money and resources to have emergency back up battery power. All you need is a whole house generator fueled with LPG or diesel. No rewiring of your home, 1/5th the cost of battery and special inverter, can run everything in your home including air conditioning, heat, and hot water. Like nothing ever happened.

What really tops the cake is if you go Hybrid with battery back up requires a generator. Why on earth throw all that money away with batteries, expensive inverter, and rewiring your home?

Psst. You will not be running a Window Shaker with batteries, you get to suffer like everyone else. Second point: Where will your panels going to be after a Hurricane? You could attach them to a rope and fly them like a kite during the Hurricane to pass time and wait out the storm.

[ChrisOlson]

What a horrible waste of money and resources to have emergency back up battery power.

Actually, there is a solid reason for it. The vast majority of residential standby generators get most of their hours accumulated over a 10 year period thru their automatic exercise routine. They only get used once in a blue moon for an actual power outage. A small inverter/battery/solar backup system can be used every single day to offset your critical loads. So you get more use out of your investment with the battery-based backup system than you do from a generator. Over a five year period of bi-weekly 30 minute exercise runs a LPG generator easily costs more to maintain than a small bank of batteries. And during an actual power outage it can easily cost $150 per DAY to run a whole-house genset.

Standby generators are sized to run at no greater than 50% of their rated continuous load, which is the absolute worst efficiency level for a genset. With a battery-based inverter backup system you can use a much smaller generator operating at much higher efficiency, loaded to 80% or greater of its rated continuous load, and it only has to run part of the time.

[jimindenver]

I know that the people with automatic LG generators didn't fair so well in the flood areas last year, they turned off the gas to the areas for months.

[ChrisOlson]

Natural gas is the absolute worst fuel choice for a standby generator. It is the first fuel to be lost in a widespread power outage. LPG is also a poor choice since you cannot store enough on-site for an extended outage and delivery of it is halted in an emergency situation. Remember that a whole-house generator will burn 3.0-3.5 gal/hr of LPG. Even a full 500 gallon tank will only last a little over 100 hours.

Diesels are generally a poor choice for residential standby power. Diesel generators have special starting and loading requirements to prevent them from wet-stacking and are best suited to larger, or load controlled, applications. Diesel fuel is generally available in a disaster situation, but is not as readily available as gasoline.

Gasoline is the best choice for most folks. It is the most widely available fuel and even in a total outage there are all kinds of cars sitting around with gasoline in the tanks that can be used in a genset. During hurricane Sandy, after all the stationary gensets quit or ran out of fuel, the gasoline fueled portables were the only ones still running after the first week:

[foo1bar]

That's a lot of items on that wall....
I think I see at least 3 different breaker panels.
I really hope that you've spent some time documenting that - and put the documentation in a spot where your spouse knows where it is (and/or your heirs know where it is for when they sell your house)

[ChrisOlson]

Our system has gone thru three inverter upgrades and stuff was added on with time. If I did it from a fresh start I would put in a XW Load Center. But instead, the last time we upgraded the inverter, the generator was started and whole-house loads switched over to gen power with the transfer switch. Then the inverter and DC system shut down while the new inverter was installed. We were on gen power for two days during the swap.

Rather than put in a 200A panel and rewire everything, we kept adding 100A SquareD QO load centers until now we got three of them. Actually, one (the one closest to the inverter) is AC bypass with a QODTI-2 interlock and water heating, the top panel on the left is 240V distribution to sub panels in the house and my shop, the bottom is 120V distribution that was original for our first 120V inverter. They can all be switched to whole-house genset power with the Ronk transfer switch way to the left, which disconnects the standby generator from the inverter's AC2 input and connects it to the distribution panels.

The Outback PSX-240 autotransformer is used for connecting a 120V generator to our split-phase system, and for balancing the legs on the standby generator when it is on whole-house loads. We have three generators with more transfer switches and contactors in the generator room to connect whichever generator to the system is needed. Two of them are automatic start with auto failover, controlled by the XW AGS. The third is manual start only. When we originally put in the XW split-phase inverter, I used the autotransformer to balance the inverter and genset, but then found out the XW can do that by itself. The XW will run unbalanced loads on L1 and L2, and will keep the generator legs in perfect balance without the autotransformer with a feature it has called Generator Support Plus where it connects the genset neutral to the centertap of its transformer. So I rewired the autotransformer after discovering that.

It all works very well. It is a 30 kWh/day system and if you came to visit our place you can't tell that we don't have utility power - except for the fact that the system starts and stops generators as needed if the inverter overloads, or we end up with not enough solar and wind power, etc.. We don't mess with anything - it is pretty much 100% maintenance free, and totally automatic other than having to change oil in the gensets now and then. Over a year's time the gensets provide about 14% of our total power needs, more in the winter, less in the summer.

Just an example of what CAN be done with a hybrid system if you have the money to do it.

My wife and I know it like the back of our hand. When we pass on and our heirs have to figure it out - good luck. We don't really care at that point.

[SunEagle]

Our system has gone thru three inverter upgrades and stuff was added on with time. If I did it from a fresh start I would put in a XW Load Center. But instead, the last time we upgraded the inverter, the generator was started and whole-house loads switched over to gen power with the transfer switch. Then the inverter and DC system shut down while the new inverter was installed. We were on gen power for two days during the swap.

Rather than put in a 200A panel and rewire everything, we kept adding 100A SquareD QO load centers until now we got three of them. Actually, one (the one closest to the inverter) is AC bypass with a QODTI-2 interlock and water heating, the top panel on the left is 240V distribution to sub panels in the house and my shop, the bottom is 120V distribution that was original for our first 120V inverter. They can all be switched to whole-house genset power with the Ronk transfer switch way to the left, which disconnects the standby generator from the inverter's AC2 input and connects it to the distribution panels.

The Outback PSX-240 autotransformer is used for connecting a 120V generator to our split-phase system, and for balancing the legs on the standby generator when it is on whole-house loads. We have three generators with more transfer switches and contactors in the generator room to connect whichever generator to the system is needed. Two of them are automatic start with auto failover, controlled by the XW AGS. The third is manual start only. When we originally put in the XW split-phase inverter, I used the autotransformer to balance the inverter and genset, but then found out the XW can do that by itself. The XW will run unbalanced loads on L1 and L2, and will keep the generator legs in perfect balance without the autotransformer with a feature it has called Generator Support Plus where it connects the genset neutral to the centertap of its transformer. So I rewired the autotransformer after discovering that.

It all works very well. It is a 30 kWh/day system and if you came to visit our place you can't tell that we don't have utility power - except for the fact that the system starts and stops generators as needed if the inverter overloads, or we end up with not enough solar and wind power, etc.. We don't mess with anything - it is pretty much 100% maintenance free, and totally automatic other than having to change oil in the gensets now and then. Over a year's time the gensets provide about 14% of our total power needs, more in the winter, less in the summer.

Just an example of what CAN be done with a hybrid system if you have the money to do it.

My wife and I know it like the back of our hand. When we pass on and our heirs have to figure it out - good luck. We don't really care at that point.

I think your system looks just fine for one that has grown over the years without much in the way of outages for you. If you can get to a part and replace it without removing a wall then you are ok.

My only suggestion would be not to put that coffee cup on top of one of those panel boards. Fluid and electricity don't like each other.

[ChrisOlson]

I think your system looks just fine for one that has grown over the years without much in the way of outages for you. If you can get to a part and replace it without removing a wall then you are ok.

Oh yeah, we can replace or repair anything, with enough redundancy to keep power on by simply rerouting generators with either the Ronk transfer switch or the AC Bypass on the inverter. My thoughts were that in the event the inverter needs to come down for service, or to replace a board in it or whatever - you want to be able to keep the power on but have everything in the inverter dead. The normal way of hooking these off-grid hybrid systems up is to feed the inverter's AC2 input with the generator. Which is fine unless you have to take the inverter offline for service. With the genset feeding the AC2 you still have hot power in the inverter and its associated panel, even with an AC bypass. So I designed our system to be able to eliminate that, and at the same time disconnect the generators from system control to be able to operate them manually.

We have had one power outage with our new system. I was upgrading firmware in one of the system components, and of course sitting in my office at the computer when doing it. I uploaded the firmware file and this warning popped up on my screen (that I didn't read). I just clicked on "Upgrade". The power instantly went out. The battery in my laptop is no good so even that went out and I lost contact with the power system.

I sort of went "F & ^ K K K k !!!!!" when I realized what I had done. The system had gone into standby to update the component. I fumbled my way out of my office in the dark and made it to the kitchen where I could see light from our Android tablet computer that's on the wall there, and which was running on battery power. When I went by the living room in the dark my wife asked, "What did you do now?" I just said, "I didn't do nuthin so get off my back." She replied with, "Yeah right - you're always doing something." I made it to the power room and was fumbling around trying to find a flashlight, and I found one but the batteries in it were dead. Our power never goes out, so who needs batteries in the flashlight?

I was fumbling in the dark for the transfer switch lever and was then going to feel my way to the generator room about 150 feet from the house and see if I could get a genset started and bring it online. Just as I was ready to flip the transfer switch lever the power came back on. The firmware upgrade was complete so it brought the system back online. As I walked by the living room when I went back in the house, I told my wife in my most professional way I could muster, "Fixed it......" She wasn't particularly impressed and was looking at me with a suspicious frown. So I thought I'd better escape before I had to answer too many more questions.

[SunEagle]

Oh yeah, we can replace or repair anything, with enough redundancy to keep power on by simply rerouting generators with either the Ronk transfer switch or the AC Bypass on the inverter. My thoughts were that in the event the inverter needs to come down for service, or to replace a board in it or whatever - you want to be able to keep the power on but have everything in the inverter dead. The normal way of hooking these off-grid hybrid systems up is to feed the inverter's AC2 input with the generator. Which is fine unless you have to take the inverter offline for service. With the genset feeding the AC2 you still have hot power in the inverter and its associated panel, even with an AC bypass. So I designed our system to be able to eliminate that, and at the same time disconnect the generators from system control to be able to operate them manually.

We have had one power outage with our new system. I was upgrading firmware in one of the system components, and of course sitting in my office at the computer when doing it. I uploaded the firmware file and this warning popped up on my screen (that I didn't read). I just clicked on "Upgrade". The power instantly went out. The battery in my laptop is no good so even that went out and I lost contact with the power system.

I sort of went "F & ^ K K K k !!!!!" when I realized what I had done. The system had gone into standby to update the component. I fumbled my way out of my office in the dark and made it to the kitchen where I could see light from our Android tablet computer that's on the wall there, and which was running on battery power. When I went by the living room in the dark my wife asked, "What did you do now?" I just said, "I didn't do nuthin so get off my back." She replied with, "Yeah right - you're always doing something." I made it to the power room and was fumbling around trying to find a flashlight, and I found one but the batteries in it were dead. Our power never goes out, so who needs batteries in the flashlight?

I was fumbling in the dark for the transfer switch lever and was then going to feel my way to the generator room about 150 feet from the house and see if I could get a genset started and bring it online. Just as I was ready to flip the transfer switch lever the power came back on. The firmware upgrade was complete so it brought the system back online. As I walked by the living room when I went back in the house, I told my wife in my most professional way I could muster, "Fixed it......" She wasn't particularly impressed and was looking at me with a suspicious frown. So I thought I'd better escape before I had to answer too many more questions.

Yeah. Best to pick your fights or hide before the SHTF.

I hate software updates. It usually takes me hours to get a program working the way I had it since most updates put you back to the vanilla default version of a control panel.

I use to have to go look for that "working" flashlight when the power went out. Now since I carry a droid cell phone I have a built in flashlight app that is always available.

[Sunking]

Natural gas is the absolute worst fuel choice for a standby generator. It is the first fuel to be lost in a widespread power outage.

Agree that is why hardly anyone uses it. NG is fine and works outside of hurricane and earthquake areas.

LPG is also a poor choice since you cannot store enough on-site for an extended outage and delivery of it is halted in an emergency situation. Remember that a whole-house generator will burn 3.0-3.5 gal/hr of LPG. Even a full 500 gallon tank will only last a little over 100 hours.

Completely false statement. 8 to 10 Kw LPG generators burn 30 to 45 CFH of fuel which translates to about 1 gallon look it up. A week has 168 hours. For LPG 1 gallon of of fuel = 35.65 cubic feet. Since a Honda 5 Kw generator burns roughly 1 gallon per hour your argument does not hold water.

Check it out on both Kohler and Generac web site. I would post a link, but the forum will not allow me to anymore. Both allow you to compare all models and fuel burn rate is included in the specs. Or are you calling them and me liars?

Diesels are generally a poor choice for residential standby power. Diesel generators have special starting and loading requirements to prevent them from wet-stacking and are best suited to larger, or load controlled, applications. Diesel fuel is generally available in a disaster situation, but is not as readily available as gasoline.

Another completely false statement. Diesel and LPG are the only fuels available during wide spread power outages. As anyone knows those fuels are delivered by distributors in trucks to your location. All one has to do is call their supplier who gave you the free tank to store the LPG in. All it takes is a phone call or visit. Why can you call when their is no electricity? Because phone and cell companies use LPG and Diesel generators. LPG is primary fuel for all cell towers followed by diesel which have absolutely no problems getting fuel during storm recovery. They get it from the same distributors a home owner does. A 550 gallon LPG tank runs a cell site generator for a week or more and they use more power than a home. My genny back in TX can go two weeks and more if I cycle the generator.

A pro with real experience should know that don't you think?

---Mod Note: Dereck, your original post was assigned for moderation because of the link in it, so that is why you could not see it. I have deleted that first post as a duplicate, and here is the link to Kohler generators that you had in the first post:

Kohler 8 to 10 Kw generators Check it out

[ChrisOlson]

Completely false statement. 8 to 10 Kw LPG generators burn 30 to 45 CFH of fuel which translates to about 1 gallon look it up.

ROTFLMAO! A 8-10 kW generator is not a whole-house genset. Take a look at a Cummins-Onan RS20 with auto load management. That's a whole-house generator and even then it is less than half of a normal 200A service.

[sdold]

ROTFLMAO! A 8-10 kW generator is not a whole-house genset.

I'm surprised by that, the most power usage I've ever seen on our meter with the wife and kids running the A/C and having all kinds of crap on in the house is about 6 KW. I would have thought 8 KW would be acceptable and 10 KW would be plenty. I have a 200A panel but I'd never use anything close to 48 KW.

[ChrisOlson]

I'm surprised by that, the most power usage I've ever seen on our meter with the wife and kids running the A/C and having all kinds of crap on in the house is about 6 KW. I would have thought 8 KW would be acceptable and 10 KW would be plenty. I have a 200A panel but I'd never use anything close to 48 KW.

You have to understand the rating system on standby generators (vs prime). The nameplate rating on cheap LPG-fueled residential generators like from Kohler or Generac only have a 500hr design life expectancy. That nameplate rating is not what they can produce continuous. 50% of their nameplate rating is max continuous. So a "10 kW" generator is really only a 5 kVA unit and it will not maintain voltage and freq +/-5% on surge loading/unloading above 50% nameplate. This is why either Kohler or Generac will void the warranty on their residential standy generators if used on an off-grid installation, because in off-grid applications we load them to 80% nameplate or better - OR buy units that actually have a prime power rating. For example, the Honda EM4000SX generator that we have for our off-grid installation is rated at 3.6 kVA prime, 4.0 kVA standby for 30 minutes, 5.0 kVA overload for 20 seconds. And it maintains PERFECT voltage/freq regulation +/- 1% even at full overload capacity. This is a quality generator and they are very expensive compared the Box Store cheapies.

The other thing is your home's electrical requirements. Not all are the same. But, for instance, if you have a large heat pump a 10 kW Generac will not start it while carrying baseline loads. Say you have 1.5 kVA baseline, the water heater kicks in at 4.5 kVA additional load, putting the continuous to 6.0 kVA and now the 5.0 ton heat pump compressor tries to start and draws 50A @ 240V inrush. The generator is instantly snuffed and your power goes out.

Generac and Kohler sell their cheap residential standbys with transfer switches (like the Generac EZ Switch) that are designed to only power part of your home in an outage. They are critical circuit backup only - not whole home. Minimum for whole-home with any type of A/C unit larger than 3.0 ton, resistance or heat pump heating, and electric water heating is 20 kVA. Before purchasing any generator for partial or whole-home backup you should consult with a generator professional, on-site, to evaluate your particular installation to ensure that you do not buy the wrong unit. A quality residential whole-house unit like a Cummins-Onan RS20 will cost you in the neighborhood of $20,000 installed.